The present invention refers to roller bearings with the ability to sense and determine a bearing load in magnitude as well as in direction.
In many applications where primarily large roller bearings are used, it is, from an aspect of process control, of great interest to be able to determine the momentary load of the bearing. Thus, one can, for example, with knowledge about the bearing load in an ore mill, control the degree of filling of the mill to be at an optimal level from a mining operation perspective. Further, it is possible to continuously monitor the condition of the bearing by means of the bearing load, since deviations from normal values may indicate different error functions or damage in the bearing.
For such purposes there have previously been suggested different types of force measurement bearings where the forces and loads are measured with strain gauge transducers located at the inner and/or the outer ring of the bearing. By influence of changing loads, which occur during operation, these strain gauge transducers obtain a measurable change of electric resistance of the transducer whereby load variations, according to the principle of an amplitude modulated carrier frequency system, generate a carrier frequency the amplitude of which represents the measurement value. This means that the rings have to be provided with a great number of strain gauge transducers, and at the same time a relatively complicated and thereby costly calibration of the bearing is required. Also, there are certain imperfections in these prior systems, which are known for example through U.S. Pat. No. 4,203,319.